Lei Li,Han Lu,Yuling Xue,Yannan He,Baohua Zhao,Lianzhong Ai,Shijie Wang
Probiotic fermented milk has emerged as a prominent functional food for its substantial role in promoting intestinal health and overall wellness. However, a persistent challenge in the industry is post-acidification, a process where lactic acid bacteria continue fermenting during storage, leading to excessive acidity, textural degradation, and flavor alterations. This study focuses on the identification and characterization of a naturally mutated strain of Lacticaseibacillus paracasei capable of significantly attenuating post-acidification in fermented milk. A novel mutation was discovered in the α-glucosidase gene (AF91_03255), wherein the substitution of arginine at position 477 with glycine altered the enzyme's binding dynamics. This mutation enhanced binding stability between the enzyme and its substrate by approximately 16.8%, indirectly modulating acid production without directly limiting glucose metabolism. Through a combination of multi-omics techniques, including metabolomics and genomic sequencing, this study revealed significant shifts in the glycerophospholipid metabolic pathway, suggesting alterations in cell membrane composition as a core mechanism. Additionally, comparative analyses between the wild-type and mutant strains demonstrated notable differences in acid production, viable cell counts, and storage stability. The mutant strain maintained a higher pH and reduced titratable acidity during extended storage while preserving bacterial viability, distinguishing it from traditional approaches reliant on additives or processing modifications. The findings underscore the potential of α-glucosidase as a pivotal target for post-acidification regulation in fermented milk products. Furthermore, this work contributes valuable insights into the strain improvement strategies essential for advancing the stability and sensory qualities of fermented milk.
Protein-stabilized high internal phase emulsions (HIPEs), which are pseudoplastic fluids with shear thinning and high viscoelasticity, are suitable for 3D printing inks. However, owing to the lack of a universal approach to the 3D printing of HIPEs, existing printing materials are unable to meet the developmental, biocompatibility, and safety requirements of various applications. Herein, it is demonstrated that post-acidification of protein HIPEs enhances 3D printing performance. This method has the advantage of breaking through protein limitations, pH, and other environmental factors. The self-supporting property required for 3D printing is achieved through the self-assembly of continuous-phase proteins into particle aggregates, and interfacial stability is maintained owing to the constant interfacial tension and contact angle. The acid-induced protein aggregates in the continuous phase do not affect the stability of the modified HIPEs. This work provides a valuable new idea for advancing the application of protein HIPEs in 3D printing through a post-acidification strategy.
To control the post-acidification caused by the continued fermentation of Lactobacillus in fermented apple juice (FAJ) during cold storage and establish a shelf-life prediction model of the post-acidification process, the effects of nisin and ε-polylysine on the physicochemical and microbiological properties of FAJ during cold storage were evaluated. In addition, quality indexes and shelf-life prediction models of fermented apple juice with the addition of nisin (FAJN) were established and verified. The post-acidification control effect of 40 mg/L nisin was determined to be optimal. Furthermore, deterioration of quality indicators of FAJ treated with 40 mg/L nisin was significantly controlled, and the shelf-life was prolonged compared with FAJ. Prediction models of L*, a*, b*, ΔE, viable cell count, and the stability coefficient of FAJN were established and verified, and a shelf-life prediction model was established with the number of viable bacteria as the prediction indicator. Relative errors between the predicted and measured values of each model were within ±10%, indicating that the models could predict changes in each index and the shelf-life of FAJN when stored at 4 °C and 25 °C.
危险品化学品经营许可证（带存储）